This invention relates generally to a speed governor and in particular, to a braking device for a rotary shaft.
While the present invention is suitable for general application as described above, it is particularly well-suited for use with passenger loading bridges for aircraft. These bridges utilize an electrical motor and gear box chain drive to a ball screw to provide vertical movement to the bridge. The present systems do not have a safety provision to stop the bridge from going completely down to the bottom limit of the vertical drive column in case of failure of the brake of the electrical motor, chain, or gear box. The abrupt dropping of the bridge can cause injury to passengers as well as damage to the aircraft.
Other centrifugal force speed governors have previously been disclosed. These are exemplified by U.S. Pat. Nos. 3,715,016 to Frieder, 2,388,046 to Beall, and 3,415,343 to Svensson.
However, the prior art braking devices have been quite large, complicated, slow to respond, and require disassembly of the system for resetting once the problem has been corrected.